Method for creating an air pressure

ABSTRACT

This invention provides a method of creating air pressure by generating a source of air pressure greater than atmosphere air pressure from a first rotary screw compressor. The first rotary screw compressor has a first displacement and is driven by a first power source. The generated source of air pressure from the first rotary screw compressor is directed to a second rotary screw compressor having a second displacement which is less than the first displacement and which is driven by a second power source which is independent of the first power source. The generated air pressure from the second rotary screw compressor driven by the second power source is greater than 200 psi.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This is a continuation-in-part application of application Ser. No. 10/139,106, filed May 3, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a method for creating an air pressure greater than 200 psi. The invention utilizes air compressors that are driven by a power source to create a desired discharge air pressure greater than 200 psi.

[0004] 2. Description of the Related Art

[0005] There has been a need to increase air pressure produced from existing rotary screw compressors. Equipment such as a reciprocating booster is available to produce in excess of 200 psi air pressure. Air pressure is produced from a number of primary rotary screw compressors that take air in at atmospheric pressure and increases it to between 100-350 psi air pressure. This compressed air is then collectively fed to a reciprocating booster which produces an output in excess of 200 psi (or 350 psi depending on the air pressrure from the primary rotary screw compressor). This equipment, namely the primary rotary screw compressors that are used and the reciprocating booster each have their own separate power source.

[0006] A common example of this setup would be in a typical oil or gas drilling operation where 4120 cfm of air at 500 psi is required. There would be 4 primary rotary screw compressors each creating 1070 cfm of compressed air at 350 psi for a total of 4120 cfm at 350 psi. This 4120 cfm of compressed air at 350 psi is then fed to a reciprocating booster compressor which discharges 4120 cfm of air at 500 psi.

[0007] The reciprocating booster in the above identified equipment has a considerable amount of moving components that wear and need replaced frequently. This equipment is aging and is becoming difficult to replace and to maintain because there are fewer manufacturers in the market.

[0008] Others have decided that a solution would be to scrap the primary rotary screw compressors and the reciprocating piston booster and replace it with one large two stage rotary screw compressor capable of discharging air at 500 psi with one large power source.

[0009] There is a two stage rotary screw compressor driven by one motor which is capable of producing 500 psi of air pressure. This is on the market and is being sold by Ingersoll Rand. The model is XXHP950/500. It has a rated speed of 1800 rpm driven by a 3412DIPA Engine; rated at 560 horsepower.

[0010] This leaves a current user who has rotary screw compressors each driven by a separate power source a choice of either trying to rebuild the reciprocating booster or scrapping the existing reciprocating booster which is useless and also scrapping otherwise serviceable, maintainable, and replaceable parts for the various primary rotary screw compressors which feed air to the reciprocating booster and replacing it with a large two stage rotary screw compressor. It is unacceptable economically to scrap existing serviceable primary rotary screw compressors.

[0011] It is also economically unacceptable to use a large two stage rotary screw stage compressor driven by one motor which is capable of producing 500 psi because in order to create the same volume of air that is needed you would need multiple two stage rotary screw compressors each producing 500 psi. So for instance in the above example of a typical oil or gas drilling operation one would need (4) 1070 cfm 500 psi two stage rotary screw compressors which is economically unfeasible.

[0012] Additionally, there are some problems with the use of a large two stage rotary screw compressor driven by one motor to produce 500 psi. One of the most significant problems that occur when generating high pressure air is the condensation of water. This is especially true when air pressure greater than 350 psi is achieved.

[0013] When hot compressed air leaves the compression chamber of a rotary screw compressor, water is held in the gas state. As the air enters the receiver tank of the compressor, it expands and cools. As this occurs the water condenses out and falls into the receiver tank where the compressor lubricant is also held. Water in the lubricant significantly reduces bearing life in a rotary screw compressor.

[0014] The current art using a two stage rotary screw compressor driven by one power source does not provide for cooling between the first and second stage of the compressor. Water condenses as the air enters the receiver tank. This water falls into the lubricant and this mixture of water and lubricant greatly reduces bearing life. In addition, the discharge air temperature of the air as it leaves the second stage of the rotary screw compressor is very hot in excess of 200 degrees Fahrenheit which reduces component life and increases the cooling requirement of the compressor oil coolers. The lubricant must be changed more often because water condenses into the lubricant and it no longer has the same lubricant qualities. In addition oil samples must be taken to determine the water content of the oil.

[0015] It is impossible to remove water from the air stream between the first and second stage by cooling in the current two stage rotary screw compressor without also removing compressor lubricant. In addition to water in the air, there is also compressor lubricant in the air between the first and second stage compressor. If the air temperature were reduced to remove the water the compressor lubricant would also be removed. The compressor lubricant needs to remain in the air mixture for lubrication and cooling as the air enters the second stage.

SUMMARY OF THE INVENTION

[0016] The inventor has developed a method that is capable of utilizing the existing primary compressors and feeding those primary compressors to another compressor which has its own power source. The additional compressor will replace the reciprocating booster and can have the same output capability as the reciprocating booster, namely greater than 200 psi and can be 500 psi or greater. The result is that the existing reciprocating booster will be replaced by a rotary screw compressor capable of providing an output in excess of 200 psi and can be 500 psi or greater.

[0017] The present invention provides a method to enable a person who already has a source of air pressure coming from primary compressors and fed to a reciprocating piston booster to produce an air pressure greater than 200 psi. Currently there is an abundance of rotary screw compressors available. There has been a need to increase the air pressure produced by the existing rotary screw compressors and the need is even greater now because of the problems associated with obtaining reciprocating booster compressors and parts for reciprocating booster compressors.

[0018] The object of this invention is to provide a method to enable a person who has an existing rotary screw compressor to produce an air pressure greater than 200 psi. This is economically advantageous because the person can use the existing equipment that has already been paid for to generate air pressure from atmosphere to up to between 100-350. The person only has to purchase another rotary screw compressor having an independent motor with enough horsepower to take the air pressure from between 100-350 to 500 psi instead of paying for expensive equipment that produces air pressure from atmosphere to 500 psi.

[0019] The inventor's solution enables one with existing primary rotary screw compressors tied to a reciprocating booster to use the primary rotary screw compressors with an additional rotary screw compressor that has its own power source independent of any power source from the primary rotary screw compressors.

[0020] Another object of the invention is to remove the water from the air and to cool the air before it enters the second rotary screw compressor and to reduce the temperature of the air generated by the second screw compressor.

[0021] The inventor's solution eliminates the significant problem of water condensation at higher pressures because water is removed by a precooler from the air before it reaches the second compressor.

[0022] This invention provides a method of creating air pressure by generating a source of air pressure greater than atmosphere air pressure from a first rotary screw compressor. The first rotary screw compressor has a first displacement and is driven by a first power source. The generated source of air pressure from the first rotary screw compressor is directed to a second rotary screw compressor having a second displacement which is less than the first displacement and which is driven by a second power source which is independent of the first power source. The generated air pressure from the second rotary screw compressor driven by the second power source is greater than 200 psi.

[0023] The generated source of air pressure from the first rotary screw compressor can be cooled by a precooler before being directed to the second rotary screw compressor. This causes the water to be condensed out of the air stream prior to it entering the second rotary screw compressor. The water can then be removed by a water separator. It also causes the air temperature being input to the second rotary screw compressor to be lowered and thus allowing a lower output air temperature from the second rotary screw compressor.

[0024] The generated source of air pressure greater than atmosphere air pressure can be passed through a separation system prior to being cooled and dried.

[0025] This invention also provides a method for creating an air pressure by generating a plurality of sources of air pressure each greater than atmosphere air pressure from a plurality of first rotary screw compressors in which together all of the first screw compressors combined have a total first displacement and in which each first compressor is driven by its own first power source. The generated sources of air pressure which are greater than atmosphere air pressure are directed to a second rotary screw compressor having a second displacement which is less than the total first displacement and which is driven by a second power source which is independent of the first power source. Air pressure greater than 200 psi is generated from the second compressor driven by the second power source.

[0026] The generated sources of air pressure greater than atmosphere can be cooled by a precooler before being directed to the second rotary screw compressor. This causes the water to be condensed out of the air stream prior to it entering the second rotary screw compressor. A water separator can then remove the water. The precooler also causes the air temperature being input to the second rotary screw compressor to be lowered and thus allowing a lower output air temperature from the second rotary screw compressor.

[0027] The generated source of air pressure greater than atmosphere air pressure can be passed through a separation system prior to being cooled and dried.

[0028] This invention also provides a method for creating an air pressure of at least 500 psi by generating a first air pressure of at least 167 psi. The first air pressure of at least 167 psi is cooled to remove moisture (i.e. water) and to cool the first air pressure. Water can be removed from the first air pressure of at least 167 psi. A rotary screw compressor with a 3:1 or less discharge to suction compression ratio having its own lubrication system and a power source is provided. The rotary screw compressor is used to increase the cooled first air pressure to at least 500 psi. The rotary screw compressor's power source can be an engine of a carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1A diagrammatic rendition of the flow of one embodiment of the method;

[0030]FIG. 2A second diagrammatic rendition of the flow of another embodiment of the method;

[0031]FIG. 3A third diagrammatic rendition of the flow of another embodiment of the method; and

[0032]FIG. 4A fourth diagrammatic rendition of the flow of another embodiment of the method.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Definitions

[0033] Air pressure—pressure measured in pounds per square inch (p.s.i.) that air exerts on an object.

[0034] Generating a source of air pressure—a means of producing air at a pressure greater than atmospheric pressure using an air compressor which can be a rotary screw compressor.

[0035] Greater than atmosphere—an air pressure that is higher than atmospheric pressure which is 14.7 lbs. per square inch at sea level.

[0036] Rotary screw compressor—an air compressor consisting of a male and female rotor. As the male rotor is driven, it rotates into the female rotor and displaces a specific volume of air. This can be a single or two stage compressor.

[0037] Displacement—the volume of air measured in cubic feet per minute that is displaced by rotating male and female rotors in a compressor.

[0038] Power source—the engine or motor that is driving the rotary screw compressor.

[0039] Directing the generated source of air pressure—providing a path for air to flow from a first rotary screw compressor to a second rotary screw compressor or from primary screw compressors to the second rotary screw compressor.

[0040] Less than the first displacement—the volume of the 2^(nd) rotary screw is less than the volume of the 1^(st) rotary screw.

[0041] Independent of the first power source—having it's own source of power not connected in any way.

[0042] Plurality of first rotary screw compressors—more than one first rotary screw compressor there may be many first rotary screw compressors.

[0043] Total first displacement—the total displacement or sum of all the displacements of the first rotary screw compressor or compressors.

[0044] Its own first power source—a source of power for a first rotary screw compressor.

[0045] Two stage compressor—a compressor having two compression chambers, one compression chamber being smaller than the other.

[0046] Reciprocating booster—a piston compressor that takes in air from another compressor and increases the pressure of that air.

[0047] Primary rotary screw compressor—refers to any or all of the first rotary screw compressors used to supply air to the second rotary screw compressor. It is an air compressor that takes in air at atmosphere pressure and has a discharge air pressure rating up to around 350 psi. It can be a single or two stage compressor. It can also be a single compressor or a plurality of compressors.

[0048] Regulating/loading and unloading system—a system on an air compressor that regulates speed of a power source, discharge pressure, inlet pressure, discharge volume, and inlet volume. The regulated variables are all interrelated and interconnected.

[0049] Separation system—The system on an air compressor that removes oil from an air/oil mixture in a receiver tank before the air is discharged from the compressor.

[0050] Cooling system—The system on an air compressor that cools a compressor lubricant before it is reintroduced into the compressor. Included in this system is a Filtration system for removing contaminants from the oil.

[0051] Lubrication system—The systems on an air compressor which is responsible for adequate lubrication of the compressor.

[0052] Receiver Tank—A tank located on an air compressor that holds a compressed air/oil mixture and also contains a filter to remove the oil from the air.

[0053] Discharge air pressure—A pressure of air after the air leaves the receiver tank.

[0054] An engine of a carrier—The power source which provides horsepower to operate the carrier which can be a truck. This engine is separate from any deck mounted engine which may be mounted on the carrier.

[0055] Generating a first air pressure of at least 167 psi—Air pressure created by a primary compressor.

[0056] Cooling and removing water—Process whereby air, after being compressed, is piped or plumbed through the tubes on a precooler. Air is then forced over the tubes in the precooler by a fan. The compressed air is cooled as it travels from inlet to outlet in the precooler. As the air is cooled the water condenses out and is removed by a condensate trap.

[0057] Remove moisture—Eliminating a majority of water from the compressed air.

[0058] Cool the first air pressure—Reducing the temperature of the first air pressure.

[0059] 3:1 or less discharge to suction compression ratio—Ratio of the discharge pressure to the inlet pressure. It can be 3:1, 2:1, or any range less than 3:1.

[0060] To cool—reducing the air temperature

[0061] Cause water to condense out—creating condition by which water will be removed from an air stream

[0062] Water Separator—A mechanical device that removes water from an air water/water mixture by using centrifugal force to spin out water

DESCRIPTION

[0063]FIG. 1. is a block diagram of a method for generating air pressure which shows a first rotary screw compressor 2 having a first power source 4. The first rotary screw compressor 2 may be called a primary compressor. The first rotary screw compressor 2 generates a source of air pressure 6 which is greater than atmosphere pressure and which is directed to a second rotary screw compressor 8 having a second independent power source 10. The second rotary screw compressor 8 has a discharge air pressure 12 that is greater than 200 psi.

[0064]FIG. 2. is a block diagram of a method for generating air pressure showing a plurality of first rotary screw compressors 2 each having its own first power source 4. The first rotary screw compressors 2 can be referred to as primary compressors. The first rotary screw compressors 2 have a combined total first displacement. Each of the first rotary screw compressors 2 generates a source of air pressure 6 which is greater than atmosphere pressure. Each source of air pressure 6 is directed to a single second rotary screw compressor 8 having a displacement which is less than the total first displacement. The second rotary screw compressor has a second independent power source 10. The second rotary screw compressor 8 generates discharge air pressure 12 which is greater than 200 psi.

[0065]FIG. 3. is a block diagram of a method for generating air pressure which shows a first rotary screw compressor 2 having a first power source 4. The first rotary screw compressor 2 may be called a primary compressor. The first rotary screw compressor 2 generates a source of air pressure 6 which is greater than atmosphere pressure and which is directed to a precooler 14 that reduces the air temperature. Water condenses out of the air as the temperature is reduced. A water separator 15 removes the water so that there is a cooled and dried source of air pressure greater than atmosphere 16. The cooled and dried source of air pressure greater than atmosphere 16 is directed to a second rotary screw compressor 8 having a second independent power source 10. The second rotary screw compressor 8 has a discharge air pressure 12 which is greater than 200 psi.

[0066] The source of air pressure 6 generated by the first rotary screw compressor 2 can be at least 167 psi. The precooler 14 can cool the source of air pressure 6 to remove moisture and to cool the first air pressure 6. The second rotary screw compressor 8 can be a compressor with a 3:1 or less discharge to suction compression ratio having its own lubrication system and having a second independent power source 10. The second independent power source 10 can be an engine of a carrier. For example, a crane carrier has its own engine used to power the drive train of the carrier. This can be used to provide power to the second rotary screw compressor 8. The second rotary screw compressor 8 is used to increase the cooled and dried source of air pressure greater than atmosphere 16 to at least 500 psi.

[0067]FIG. 4. is a block diagram of a method for generating air pressure showing a plurality of first rotary screw compressors 2 each having its own first power source 4. The first rotary screw compressors 2 can be referred to as primary compressors. The first rotary screw compressors 2 have a combined total first displacement. Each of the first rotary screw compressors 2 generates a source of air pressure 6 which is greater than atmosphere pressure. Each source of air pressure 6 is directed to a single precooler 14 designed to handle the volume and pressure of the air coming from the primary compressors that reduces the air temperature. The sources of air pressure could alternatively be directed to multiple precoolers (not shown in drawings) that reduce the air temperature. Water is condensed out of the air as the temperature is reduced. A water separator 15 removes the water so that there is a cooled and dried source of air pressure greater than atmosphere 16. The cooled and dried source of air pressure greater than atmosphere 16 is directed to a second rotary screw compressor 8 having a displacement which is less than the total first displacement. The second rotary screw compressor has a second independent power source 10. The second rotary screw compressor 8 generates discharge air pressure 12 which is greater than 200.

[0068] The above embodiments can also have a regulating/loading and unloading system, a separation system, a cooling system, and/or a lubrication system. These additional systems can operate in a similar manner to the current systems used in existing air compressors.

[0069] Most existing rotary screw compressors have a lubrication system and a separation system. The lubrication system injects oil into the compressor for lubrication and cooling. Thus as the compressed air leaves the compressor it contains oil. The separation system removes a vast majority of the oil from the compressed air before the compressed air is discharged.

[0070] In FIGS. 3 and 4 it is beneficial for the first rotary screw compressor 2 or the plurality of first rotary screw compressors 2 to have a lubrication system and a separation system and for the second rotary screw compressor 8 to have its own lubrication and separation system. If the primary compressors are equipped as described then oil has been removed from the source of air pressure greater than atmosphere pressure 6. This enables the precooler 14 to remove water only. The second rotary screw compressor 8 if equipped as described above has its own lubrication system that adds oil into the second rotary screw compressor. The separation system for the second rotary screw compressor 8 removes oil from the discharge air pressure greater than 200 psi 12.

[0071] The following is one example of how the invention could be practiced:

[0072] 1) Connecting the generated source of air pressure from two 1070 CFM/350 psi (two stage) compressors each powered by a 465 hp engine and having a separation system and a lubrication system to produce one source of air pressure which is 2140 CFM at 350 psi;

[0073] 2) Directing the combined source of air pressure to a precooler designed to handle volume and pressure of air coming from the primary compressors thereby reducing the temperature so that a majority of the water is condensed from the air and the water is then removed by a water separator; and

[0074] 3) Directing the cooled and dried generated source of air pressure to a second rotary screw compressor having an independent power source. The second rotary screw compressor compresses the air which is at 350 psi to 500 psi, and discharges air at 500 psi.

[0075] Various changes could be made in the above construction and method without departing from the scope of the invention as defined in the claims below. It is intended that all matter contained in the above description as shown in the accompanying drawings shall be interpreted as illustrative and not as a limitation. 

I claim:
 1. A method for creating an air pressure comprising: (a) generating a source of air pressure greater than atmosphere air pressure from a first rotary screw compressor having a first displacement and which is driven by a first power source; (b) directing the generated source of air pressure greater than atmosphere air pressure to a second rotary screw compressor having a second displacement which is less than the first displacement and which is driven by a second power source which is independent of the first power source; and (c) generating an air pressure greater than 200 psi from the second compressor driven by the second power source.
 2. The method as recited in claim 1 further comprising cooling and removing water from the source of air pressure greater than atmosphere before it is directed to the second rotary screw compressor. 3 The method as recited in claim 2 further comprising passing the source of air pressure greater than atmosphere through a separation system prior to cooling and removing water from the source of air pressure greater than atmosphere.
 4. The method as recited in claim 1 including using a precooler to cool the source of air pressure greater than atmosphere that will cause water to condense out.
 5. The method as recited in claim 4 including using a water separator to remove water that has been condensed out.
 6. A method for creating an air pressure comprising: (a) generating a plurality of sources of air pressure each greater than atmosphere air pressure from a plurality of first rotary screw compressors in which together all of the first rotary screw compressors combined have a total first displacement and in which each first compressor is driven by its own first power source; (b) directing the generated sources of air pressure greater than atmosphere air pressure to a second rotary screw compressor having a second displacement which is less than the total first displacement and which is driven by a second power source which is independent of the first power source; and (c) generating an air pressure greater than 200 psi from the second compressor driven by the second power source.
 7. The method as recited in claim 6 further comprising cooling and removing water from the sources of air pressure greater than atmosphere before it is directed to the second rotary screw compressor.
 8. The method as recited in claim 7 further comprising passing the source of air pressure greater than atmosphere through a separation system prior to cooling and removing water from the source of air pressure greater than atmosphere.
 9. The method as recited in claim 6 including using a precooler to cool the source of air pressure greater than atmosphere that will cause water to condense out.
 10. The method as recited in claim 9 including using a water separator to remove water that has been condensed out.
 11. A method for creating an air pressure of at least 500 psi comprising: (a) generating a first air pressure of at least 167 psi; (b) cooling the first air pressure of at least 167 psi to remove moisture and to cool the first air pressure; (c) providing a rotary screw compressor with a 3:1 or less discharge to suction compression ratio having its own lubrication system and a power source; and (d) using the rotary screw compressor to increase the cooled first air pressure to at least 500 psi.
 12. A method as recited in claim 11 wherein the power source is an engine of a carrier. 